Towards standardization in microdosimetry: Addressing stochastic and non‐stochastic radiation interactions

Current analyses of microdosimetric experimental data and the methodologies used to interpret them often vary substantially among researchers. These discrepancies influence both the representation of microdosimetric quantities and their potential clinical applications. The necessity for progressive standardization was strongly emphasized by participants of the second Microdosimetry Workshop in 2024, as recently reported in the literature.1 With the increasing volume of work combining experimental and simulated microdosimetry, establishing a coherent framework has become more urgent. In the absence of a neutral, internationally recognized body to guide this process, a pragmatic strategy is to bring controversial topics into open discussion across virtual forums and in-person meetings. The third Workshop on Microdosimetry offers an opportunity to initiate this process by addressing selected foundational issues. The first proposed “test case” concerns the extent to which microdosimetry should be considered inherently stochastic. A central claim is that, within the constraints of clinical and therapeutic workflows, microdosimetry should prioritise non-stochastic information derived from spectra. This discussion begins with the observation that expressing a quantity through a density distribution does not, by itself, imply stochasticity. The various physical and methodological contributions to the formation of microdosimetric spectra are examined, and examples from experimental data are presented to distinguish between components reflecting stochastic behaviour and those that do not. In line with the spirit of the Workshop, this presentation is intended to stimulate collective reflection and to encourage an open and constructive debate that extends beyond the meeting itself. A preliminary list of topics for continued discussion is proposed, together with a plan to document the process, ensure inclusive participation, and provide summary reports once each topic reaches a sufficient degree of maturity.